Unit
Genetics and Evolution
Title
Bird Beak Buffet
Summary
Inspired by observations of finches on the Galapagos Islands, Charles Darwin came up with an
idea that is perhaps the most influential idea in all of science - natural selection. In this classic
activity, students learn about natural selection by becoming birds foraging for food on an island
(a large area of the schoolyard or classroom). The prey (beans) vary in their coloration such
that some blend into the environment better than others. The birds vary in the type of beak
they have (plastic forks, spoons and knives). Each season, any prey that survives has a baby
bean the same color as the parent. In addition, the most successful birds has a baby with the
same beak trait while the least successful birds die (and are reincarnated as the babies of the
successful birds). Over several generations, the bird and bean populations shift depending on
the environment. Well camouflaged beans survive and reproduce. Birds with beaks that can
easily capture beans survive and reproduce. In this way, students model natural selection in 2
species and get a very good idea of how natural selection works.
Objectives
Can explain what natural selection is and the conditions necessary for it to occur.
Can discuss changes in a population in the context of natural selection.
Can use terms such as natural selection, evolution, and adaptation scientifically.
Can organize data in a table and graph.
Can graph changes in a population over time.
Vocabulary
Trait
Population
Natural selection
Adaptation
Fitness
Evolution
Charles Darwin
Time
15-20 minutes introduction
45-50 minutes activity (The lesson plan is written so that the activity is introduced on one day
and actually done the following day. It is also possible to introduce the activity and go through
one or two years on the first day and complete the activity on the following day.)
15-20 minutes organize and summarize data
30+ minutes discussion
Grouping
Each student is a bird foraging in the same feeding ground. At the end of each year, students
gather in a group of similar-beaked birds to enter their foraging results on a clipboard. The
introduction and final discussion occurs as a whole class in a classroom.
A MyScienceBox Lesson Plan by Irene Salter (http://www.mysciencebox.org). This work is licensed under the
Creative Commons Attribution-NonCommercial License. To view a copy of this license, visit
http://creativecommons.org/licenses/by-nc/2.5/ or send a letter to Creative Commons, 559 Nathan Abbott Way,
Stanford, California 94305, USA.
** If working as a whole class in a single feeding ground is too chaotic for your students, then
this activity may be done in smaller groups of 3 or 6. Each group will get their own 1 meter
square plot of ground or even a cafeteria tray on a table in the classroom to forage in. Each
group starts with 1 or 2 representatives of each of the 3 beak types in the group and 100 beans
of each color in the feeding ground. After each season, they should summarize their data and
add new beans to their feeding ground. The bird that eats the most will reproduce and the bird
that eats the least will die and get reincarnated.**
Materials
 1 pound of red beans
 1 pound of black beans (of a similar size and shape as the other beans)
 1 pound of white beans (of a similar size and shape as the other beans)
 25 plastic forks
 25 plastic spoons
 25 plastic knives
 30 paper cups
 1 stopwatch
 1 whistle
 broom and dustpan for cleanup
 1 copy of the Bird Beak student handout for each student
 3 copies of the Bird Beak data tables
 4 clipboards with a pencil/pen tied to each
 Optional: masking tape or string to designate the borders of the feeding ground
Setting
The activity takes place in an 80 square foot (9x9 foot square) feeding ground located in the
classroom, on a concrete school yard or in a grassy field. The introduction and post-activity
discussion takes place in the classroom.
Teacher Background
Perhaps the most important idea in all of biology, or perhaps all of science, is the idea of
evolution through natural selection. This idea by Charles Darwin provides the foundation of all
of current scientific thinking in life science.
What is evolution? Quite simply, evolution is descent with modification. This includes both the
idea that the frequency of a gene will change in a population over time as environmental
conditions change and also the idea that new species descend from common ancestors over
many generations. Ultimately, evolution can explain the vast diversity of life on this planet and
the idea that all life on Earth shares a common ancestor.
Although there are many mechanisms for organisms to change over time, the most important of
these is natural selection. It works in this way:
 There is variation in a population. Different individuals have different traits.
 There is heredity. Traits can be passed on from parent to offspring through our
genes.
 There is competition (sometime referred to as differential survival and
reproduction) so that some individuals survive and reproduce more than others.
A MyScienceBox Lesson Plan by Irene Salter (http://www.mysciencebox.org). This work is licensed under the
Creative Commons Attribution-NonCommercial License. To view a copy of this license, visit
http://creativecommons.org/licenses/by-nc/2.5/ or send a letter to Creative Commons, 559 Nathan Abbott Way,
Stanford, California 94305, USA.

The end result is natural selection – the individuals with the traits that best fit
the environment are most likely to survive, reproduce, and pass on their traits to the
next generation. In this way, future generations, when viewed at the level of an entire
population, will have more advantageous traits and fewer disadvantageous traits
compared to their parents.
There are many other mechanisms for evolutionary change besides natural selection:
 Artificial selection is a common practice for humans to breed together plants or animals
with the most advantageous traits (the sweetest tomato, the most loyal dog, the fastest
horse, etc.). Thus, future generations will have more of these traits.
 Mutation can affect the distribution of traits by introducing a new trait to a population.
 Migration can rapidly change the overall distribution of traits in a population when a
group of organisms with different traits enters a new area. For example, a group of
small beaked finches is blown over to an island with primarily large beaked finches by a
hurricane.
 Genetic drift can affect a population through a random chance event – like a hurricane
or human activity – randomly destroying organisms with one trait but not another. For
instance, when a new house is constructed in a neighborhood with both red and brown
ground squirrels, it accidentally bulldozes the nest of the largest red ground squirrel
family. Suddenly, brown ground squirrels predominate.
A final important term that is often misused by students is adaptation. An adaptation is a trait
that is very well suited to a given environment that has, through natural selection, increased in
the population over many generations. Students often talk and think about adaptation as if an
organism can try to adapt or is able to get what it needs. In neither case are they correct. An
organism can’t get the genes it needs to survive by “trying”; it either has the genes or not.
Similarly, natural selection doesn’t have a goal in mind and cannot give a creature what it
“needs”; either the genes are there in the population or not.
In this activity, students come to understand natural selection, evolution and adaptation
through modeling changes in 2 populations – a population of birds with different beak traits and
a population of beans with different color traits.
Student Prerequisites
None required although an understanding of variation in traits is helpful (see Human Traits
activity or Snail Variations project).
Getting Ready
1. Purchase beans, cups and plastic utensils.
2. Make copies of the Bird Beak student handout for each student.
3. Make copies of the Bird Beak data tables. For each class that will do the activity you
should have 3 copies of “_____-Billed Bird Population Data” and 1 copies of “Bean
Population Data”. Attach these data tables to the 4 clipboards.
4. On the 3 “_____-Billed Bird Population Data” clipboards, fill in the blanks with “Fork”,
“Spoon”, and “Blade”.
5. For each class or students, count out 100 red, 100 black, and 100 white beans and mix
them together in a ziplock bag or cup.
6. Optional: mark the feeding ground boundaries with tape or string.
A MyScienceBox Lesson Plan by Irene Salter (http://www.mysciencebox.org). This work is licensed under the
Creative Commons Attribution-NonCommercial License. To view a copy of this license, visit
http://creativecommons.org/licenses/by-nc/2.5/ or send a letter to Creative Commons, 559 Nathan Abbott Way,
Stanford, California 94305, USA.
Lesson Plan
Day 1 - Introduction
1. Open class with a discussion of what human traits might help a person be more
successful (Is it an advantage to be tall? Is it an advantage in America to be blond
haired and blue eyed? How about in another country like Africa or Asia?) Leave the
interpretation of “more successful” open and somewhat vague. If this seems to
controversial for your group of students, then discuss variation in cat or dog traits and
what might help a pet survive better (Is it an advantage for a cat to be shy? Is it an
advantage for a dog to be friendly?).
2. Lead the discussion towards thinking about what “more successful” really means. Does
that mean being more popular or making more money or more likely to live happily ever
after? In scientific terms, what matters in the long run is whether you survive, find a
mate, and reproduce, passing on your genes to the next generation.
3. Introduce the activity. Pass out the handout and describe the rules.
4. Check that students understand that all the birds are of the same species but have
different beak traits. Similarly, all the beans are of the same species but have different
color traits.
5. Check that students understand that the birds that eat the most food will have a baby
with a similar beak and that the birds that eat the least will die. Similarly, surviving
beans (those not eaten) will have one baby with the same color trait.
6. Finally discuss the data collection that occurs after each round. Each student is
responsible for counting the number of each type of bean they eat and entering their
data on the bird population data clipboards. Once all the bird population data has been
gathered, then a volunteer from each group will report their data on the bean
population data clipboard.
7. If data will also be collected in lab notebooks, have students copy or paste the data
tables and graphs into their notebooks.
Day 2 – Bird Beak Buffet
1. Distribute a cup to each student. Next, give each student a plastic utensil.
2. Quickly go over the rules before heading out to the feeding ground. Make sure you bring
clipboards, beans, a stopwatch, and a whistle.
3. Place the 4 data clipboards in different locations near the feeding ground.
4. Have students stand on the edge of the feeding ground. Sprinkle the mixed beans (100
of each type) into the feeding ground.
5. Blow the whistle and give students 20 seconds to “eat” as many beans as possible. Look
out for students that cheat (have cups touching the ground, interfere with other
students, etc.) and dump out the contents of their cups or eliminate them from the
game. Blow the whistle again to signal the end of the year.
6. Each student should go to the clipboard for their beak type, count the number of beans
of each type they ate, and enter that information in the data table.
7. Each group should calculate the grand total number of beans of each type that were
eaten by their group (the bottom row of the table).
8. One volunteer from that group can bring that information to the bean population data
clipboard and enter their groups’ information. The volunteers can then help to complete
the bean data table and count out the proper number of beans to add to the feeding
ground.
A MyScienceBox Lesson Plan by Irene Salter (http://www.mysciencebox.org). This work is licensed under the
Creative Commons Attribution-NonCommercial License. To view a copy of this license, visit
http://creativecommons.org/licenses/by-nc/2.5/ or send a letter to Creative Commons, 559 Nathan Abbott Way,
Stanford, California 94305, USA.
9. While the volunteers are entering bean population data, the rest of the students should
help to sort their beans by color and return them to the stockpiles.
10. Finally, have students line up by the total number of beans they ate. Have the 5
students that ate the fewest beans act out a grisly death. (Acting out the deaths helps
students realize that they are actually dying and entering the game as a new bird with
new traits, not just trading in one tool for another.) Confiscate their utensils. Give them
new beaks that match the beaks of the 5 students that ate the most beans.
11. Have a student enter this information (the number of birds that died and number of
babies born) on the bird population data clipboards.
12. Repeat steps 5-11 for each of the next 3 years of the game for a total of 4 rounds.
13. Collect the clipboards, cups and utensils. Sweep up any remaining beans.
Day 3 – Organize, graph and discuss data
1. Create data tables on the board (or make and overhead copy) similar to the ones on the
second page of the Bird Beak Student handouts.
2. Use the information from the clipboards to fill in the summary table. Have students fill in
their tables as well.
3. Have students graph the data for each population (red beans, white beans, black beans,
fork-bills, spoon-bills, blade-bills) with years 1-5 on the x axis and the number of
organisms at the start of a year on the y axis. The graphing may be done:
o individually in their lab notebooks
o groups of 3 can each graph one bird and one bean and compare graphs as a group
o a group of students can create large poster sized graph for one of the populations to
display around the room.
4. Discuss the graphs. Notice patterns such as one population going up while another goes
down. See if the population is growing steadily or exponentially.
5. Discuss the reasons why one population did well while another did poorly. Is there a
different scenario in which a different bird or bean would do best?
6. At this point it is possible to formally address some of the vocabulary.
o Discuss natural selection – the process by which organisms with traits that best suit
the environment are most likely to survive, reproduce, and pass on their genes to
the next generation. In this activity, the bean that had the best camouflage and that
was the hardest to catch survived, reproduced, and passed on their genes.
o Discuss evolution – descent with modification, most often as the result of natural
selection. In this activity, we started with the same number of beans of each type
but ended up with the population skewed towards the beans with the best suited
traits.
o Discuss adaptation – a trait that is very well suited to a given environment that has,
through natural selection, increased in the population over many generations. In this
case, a particular color of bean could be considered an adaptation since it increased
in the population through natural selection.
7. Describe Charles Darwin’s adventures on the Beagle and how his observations
(particularly of the finches on the Galapagos Islands) led him to propose the idea of
natural selection.
8. Begin the process of busting the misconceptions that students have about evolution. See
the Understanding Evolution website
(http://evolution.berkeley.edu/evosite/misconceps/index.shtml) for a fabulous overview
of the common misconceptions students have and responses to those misconceptions.
A MyScienceBox Lesson Plan by Irene Salter (http://www.mysciencebox.org). This work is licensed under the
Creative Commons Attribution-NonCommercial License. To view a copy of this license, visit
http://creativecommons.org/licenses/by-nc/2.5/ or send a letter to Creative Commons, 559 Nathan Abbott Way,
Stanford, California 94305, USA.
9. Finally, return to the discussion you used to open this activity – what human traits might
help someone be more successful – and revisit those issues in the light of what your
students now know about natural selection and evolution. In particular, you can discuss
whether and how natural selection has worked and is still working on the human
species.
Assessment
1. Collect the students’ graphs and responses to the conclusion questions.
2. Before the activity, have students write a short essay about “what is evolution and how
does it work?” These may be collected to give you as the teacher a sense of what their
initial understanding may be. After the activity and discussion, have students revise their
essay to reflect what they now know about evolution.
Going Further
1. Conduct a deeper investigation of the Galapagos finches. There are many resources
that you can use to help you in this quest. First of all, read the Pulitzer Prize winning
book The Beak of the Finch, by Jonathan Weiner
(http://www.amazon.com/gp/product/067973337X/104-83547283538318?v=glance&n=283155). The book flips back and forth between Darwin’s original
studies and the modern day work of Peter and Rosemary Grant. The Grants have spent
over 20 consecutive years studying the Galapagos finches. They recognize each and
every finch living on the island and know the family relationships between every
individual bird. Several lesson plans for teachers have been developed from their work:
o The PBS evolution site provides a downloadable pdf file with several graphs showing
changes in finch beaks over time
(http://www.pbs.org/wgbh/evolution/library/01/6/l_016_01.html). One of PBS's
online courses addresses some of the questions raised by the data and may be
appropriate to use directly with high school students
(http://www.pbs.org/wgbh/evolution/educators/course/session4/elaborate_b.html).
o Teachers Domain has adapted the data from the PBS evolution site slightly to create
a lesson plan for teachers with discussion questions about the data.
(http://www.teachersdomain.org/9-12/sci/life/evo/finchdata/index.html)
o There is a good 1995 video of the Grants’ work called “What Darwin Never Saw”,
produced by PBS for “The New Explorer” series with Bill Kurtis. Several teacher
groups have created lesson plans that follow the video including one from ENSI web
(http://www.indiana.edu/~ensiweb/lessons/vid.wdns.html) and one from the
Chicago Academy of Sciences (http://www.chias.org/www/edu/cse/wdnhome.html).
o Finally, for the most advanced students, go straight to some original data and look
for patterns and correlations. Prentice Hall has created a lesson plan suitable for AP
Biology and college level courses looking at the effect of drought on one species of
finch.
(http://cwx.prenhall.com/bookbind/pubbooks/stiling4/chapter1/essay13/deluxecontent.html)
2. Another hands-on approach to further investigations of bird beaks is provided in this
lesson from TERC. Students use a spring scale to measure the force required to crack a
nut with pliers that represent different types of bird beaks
(http://www2.terc.edu/handsonIssues/f97/activity.html).
A MyScienceBox Lesson Plan by Irene Salter (http://www.mysciencebox.org). This work is licensed under the
Creative Commons Attribution-NonCommercial License. To view a copy of this license, visit
http://creativecommons.org/licenses/by-nc/2.5/ or send a letter to Creative Commons, 559 Nathan Abbott Way,
Stanford, California 94305, USA.
3. Finally, there are several videos that provide excellent information on evolution and
Charles Darwin.
o PBS produced a fabulous 7 episode series on evolution
(http://www.pbs.org/wgbh/evolution/). There’s excellent snippets on the evolution
of drug resistance in HIV, summaries of Darwin’s work, discussions of evolution and
religion, and more. Unfortunately, it is expensive, at $100 for the DVD set alone or
$130 for the educators’ set with curriculum.
o As part of the PBS evolution series, there are several quicktime movie clips that can
be viewed over the internet
(http://www.pbs.org/wgbh/evolution/educators/teachstuds/svideos.html) and an
associated teacher's curriculum guide with activites and lesson ideas
(http://www.pbs.org/wgbh/evolution/educators/teachstuds/tguide.html).
Sources
The Bird Beak Buffet activity is a classic in the teaching of natural selection and evolution.
There are hundreds of write ups out there with all sorts of different variations. I first learned
about the activity from Kimberly Tanner, currently faculty at San Francisco State University. I
found a box of materials to borrow from Chris Giorni of Tree Frog Treks
(http://www.treefrogtreks.com/). Then I participated in a workshop with Karen Kalamuck of the
Exploratorium Teachers’ Institute.
There



are many variations of this activity on the web from many different organizations:
USGS (http://pubs.usgs.gov/of/1998/of98-805/lessons/chpt2/act5.htm)
The National Aviary (http://www.aviary.org/curric/beaks.htm)
Understanding Evolution by the UC Museum of Paleontology has 2 versions of the lesson
Clipbirds (http://www.ucmp.berkeley.edu/education/lessons/clipbirds/) and Battle of the
Beaks (http://www.ucmp.berkeley.edu/education/lessons/birdbeaks/birdbeaks.html).
For background resources on better understanding evolution, nothing beats the Understanding
Evolution site from the UC Museum of Paleontology
(http://evolution.berkeley.edu/evosite/evohome.html). There you can find everything from
evolution 101 to scientific articles to student misconceptions to lesson plans. It’s a one-stop
resource for all a teachers’ needs.
Finally, if your school district, administrators or parents opposes the teaching of evolution, see
the National Center for Science Education (http://www.ncseweb.org) for articles and resources
that can help you justify what you are doing in your classroom.
Standards
Grade 7
Evolution
3. Biological evolution accounts for the diversity of species developed through gradual
processes over many generations. As a basis for understanding this concept:
a. Students know both genetic variation and environmental factors are causes of evolution
and diversity of organisms.
b. Students know the reasoning used by Charles Darwin in reaching his conclusion that
natural selection is the mechanism of evolution.
A MyScienceBox Lesson Plan by Irene Salter (http://www.mysciencebox.org). This work is licensed under the
Creative Commons Attribution-NonCommercial License. To view a copy of this license, visit
http://creativecommons.org/licenses/by-nc/2.5/ or send a letter to Creative Commons, 559 Nathan Abbott Way,
Stanford, California 94305, USA.
e. Students know that extinction of a species occurs when the environment changes and
the adaptive characteristics of a species are insufficient for its survival.
Grade 9-12
7. The frequency of an allele in a gene pool of a population depends on many factors and may
be stable or unstable over time. As a basis for understanding this concept:
a. Students know why natural selection acts on the phenotype rather than the genotype of
an organism.
d. Students know variation within a species increases the likelihood that at least some
members of a species will survive under changed environmental conditions.
8. Evolution is the result of genetic changes that occur in constantly changing environments. As
a basis for understanding this concept:
a. Students know how natural selection determines the differential survival of groups of
organisms.
b. Students know a great diversity of species increases the chance that at least some
organisms survive major changes in the environment.
A MyScienceBox Lesson Plan by Irene Salter (http://www.mysciencebox.org). This work is licensed under the
Creative Commons Attribution-NonCommercial License. To view a copy of this license, visit
http://creativecommons.org/licenses/by-nc/2.5/ or send a letter to Creative Commons, 559 Nathan Abbott Way,
Stanford, California 94305, USA.